2020 GMC SIERRA Electrical

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
74 Seats and Restraints
{Warning
Children who are up against,
or very close to, any airbag when
it inflates can be seriously injured
or killed. Always secure children
properly in the vehicle. To read
how, seeOlder Children 085 or
Infants and Young Children 087.
There is an airbag readiness light
on the instrument cluster, which
shows the airbag symbol.
The system checks the airbag
electrical system for malfunctions.
The light tells you if there is an
electrical problem. See Airbag
Readiness Light 0136.
Where Are the Airbags?
The driver frontal airbag is in the
center of the steering wheel.
The front outboard passenger
frontal airbag is in the passenger
side instrument panel.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
76 Seats and Restraints
When Should an Airbag
Inflate?
This vehicle is equipped with
airbags. SeeAirbag System 072.
Airbags are designed to inflate if the
impact exceeds the specific airbag
system's deployment threshold.
Deployment thresholds are used to
predict how severe a crash is likely
to be in time for the airbags to
inflate and help restrain the
occupants. The vehicle has
electronic sensors that help the
airbag system determine the
severity of the impact. Deployment
thresholds can vary with specific
vehicle design.
Frontal airbags are designed to
inflate in moderate to severe frontal
or near frontal crashes to help
reduce the potential for severe
injuries, mainly to the driver's or
front outboard passenger's head
and chest.
Whether the frontal airbags will or
should inflate is not based primarily
on how fast the vehicle is traveling. It depends on what is hit, the
direction of the impact, and how
quickly the vehicle slows down.
Frontal airbags may inflate at
different crash speeds depending on
whether the vehicle hits an object
straight on or at an angle, and
whether the object is fixed or
moving, rigid or deformable, narrow
or wide.
Frontal airbags are not intended to
inflate during vehicle rollovers, rear
impacts, or many side impacts.
In addition, the vehicle has
advanced technology frontal
airbags. Advanced technology
frontal airbags adjust the restraint
according to crash severity.
Seat-mounted side impact airbags
are designed to inflate in moderate
to severe side crashes depending
on the location of the impact.
Seat-mounted side impact airbags
are not designed to inflate in frontal
impacts, near frontal impacts,
rollovers, or rear impacts.
A seat-mounted side impact airbag
is designed to inflate on the side of
the vehicle that is struck.
Roof-rail airbags are designed to
inflate in moderate to severe side
crashes depending on the location
of the impact. In addition, these
roof-rail airbags are designed to
inflate during a rollover or in a
severe frontal impact. Roof-rail
airbags are not designed to inflate in
rear impacts. Both roof-rail airbags
will inflate when either side of the
vehicle is struck or if the sensing
system predicts that the vehicle is
about to roll over on its side, or in a
severe frontal impact.
In any particular crash, no one can
say whether an airbag should have
inflated simply because of the
vehicle damage or repair costs.
What Makes an Airbag
Inflate?
In a deployment event, the sensing
system sends an electrical signal
triggering a release of gas from the
inflator. Gas from the inflator fills the

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
122 Instruments and Controls
Power Outlets
Accessory power outlets can be
used to plug in electrical equipment,
such as a cell phone or MP3 player.
Rear of Front Center Console
The vehicle has one accessory
power outlet under the climate
control system and one accessory
power outlet on the rear of the
center console, if equipped, or on
the rear of the bench seat,
if equipped.
Lift the cover to access and replace
when not in use.
{Warning
Power is always supplied to the
outlets. Do not leave electrical
equipment plugged in when the
vehicle is not in use because the
vehicle could catch fire and cause
injury or death.
Caution
Leaving electrical equipment
plugged in for an extended period
of time while the vehicle is off will
drain the battery. Always unplug
electrical equipment when not in
use and do not plug in equipment
that exceeds the maximum
15 amp rating.
Certain power accessory plugs may
not be compatible with the
accessory power outlet and could
overload vehicle or adapter fuses.
If a problem is experienced, see
your dealer. When adding electrical equipment,
be sure to follow the proper
installation instructions included with
the equipment. See
Add-On
Electrical Equipment 0322.
Caution
Hanging heavy equipment from
the power outlet can cause
damage not covered by the
vehicle warranty. The power
outlets are designed for
accessory power plugs only, such
as cell phone charge cords.
Power Outlet 110/120-Volt
Alternating Current
If equipped, the vehicle has two
alternating current power outlets.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Instruments and Controls 123
In Cab Power Outlet and DC/ACSwitchTruck Bed Power Outlet
When the ignition is on, power is
supplied to the outlets after the DC/
AC switch is pressed. A green
indicator light on the DC/AC switch
indicates when the DC/AC operation
is active. One power outlet can be
used with electrical equipment that
uses a maximum of 400 watts.
If both outlets are being used, 400
watts will be shared between the
outlets. Ensure that all connected
devices do not exceed 400 watts.
The power outlet can be turned off
by pressing the DC/AC switch. The
power outlet can be turned back on after 10 seconds, during which the
indicator light on the switch will
flash.
An indicator light on the outlet
illuminates when power is provided
to the outlet and no system fault is
detected. The outlets will not
operate when the ignition is off, the
DC/AC switch is not pressed, or the
plug is not fully seated into the
outlet.
If equipment is connected using
more than 400 watts or a system
fault is detected, a protection circuit
shuts off the power supply and the
indicator light turns off.
Do not use a power outlet with a
missing or damaged cover.
The power outlet is not designed for
the following, and may not work
properly if they are plugged in:
.
Equipment with high initial peak
wattage, such as
compressor-driven refrigerators
and electric power tools

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Instruments and Controls 135
Uplevel English Shown, BaseLevel and Midlevel Similar
This gauge measures the
temperature of the vehicle's engine
coolant.
While driving under normal
operating conditions, if the needle
moves into the red warning area,
the engine is too hot. Pull off the
road, stop the vehicle, and turn off
the engine as soon as possible.
Voltmeter Gauge
Uplevel Shown, Base Level and Midlevel Similar
When the ignition is on, this gauge
indicates the battery voltage.
When the engine is running, this
gauge shows the condition of the
charging system. The gauge can
transition from a higher to lower or a
lower to higher reading. This is
normal. If the vehicle is operating
outside the normal operating range,
the charging system light comes on.
See Charging System Light 0138. The voltmeter gauge may also read
lower when in fuel economy mode.
This is normal.
Readings outside the normal
operating range can also occur
when a large number of electrical
accessories are operating in the
vehicle and the engine is left idling
for an extended period. This
condition is normal since the
charging system is not able to
provide full power at engine idle. As
engine speeds are increased, this
condition should correct itself as
higher engine speeds allow the
charging system to create maximum
power.
The vehicle can only be driven for a
short time with the readings outside
the normal operating range. If the
vehicle must be driven, turn off all
accessories, such as the radio and
air conditioner.
Readings outside the normal
operating range indicate a possible
problem in the electrical system.
Have the vehicle serviced as soon
as possible.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
136 Instruments and Controls
Seat Belt Reminders
Driver Seat Belt Reminder
Light
There is a driver seat belt reminder
light on the instrument cluster.
When the vehicle is started, this
light flashes and a chime may come
on to remind the driver to fasten
their seat belt. Then the light stays
on solid until the belt is buckled.
This cycle may continue several
times if the driver remains or
becomes unbuckled while the
vehicle is moving.
If the driver seat belt is buckled,
neither the light nor the chime
comes on.
Passenger Seat Belt Reminder
Light
There may be a passenger seat belt
reminder light near the passenger
airbag status indicator. See
Passenger Sensing System078.
For vehicles equipped with the
passenger seat belt reminder light,
when the vehicle is started this light
flashes and a chime may come on
to remind passengers to fasten their
seat belt. Then the light stays on
solid until the belt is buckled. This
cycle continues several times if the
passenger remains or becomes
unbuckled while the vehicle is
moving.
If the passenger seat belt is
buckled, neither the chime nor the
light comes on. The front passenger seat belt
reminder light and chime may turn
on if an object is put on the seat
such as a briefcase, handbag,
grocery bag, laptop, or other
electronic device. To turn off the
reminder light and/or chime, remove
the object from the seat or buckle
the seat belt.
Airbag Readiness Light
This light shows if there is an
electrical problem with the airbag
system. The system check includes
the airbag sensor(s), the passenger
sensing system, the pretensioners,
the airbag modules, the wiring, and
the crash sensing and diagnostic
module. For more information on the
airbag system, see
Airbag System
0 72.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
138 Instruments and Controls
Warning (Continued)
away. SeeAirbag Readiness
Light 0136 for more information,
including important safety
information.
Charging System Light
The charging system light comes on
briefly when the ignition is turned
on, but the engine is not running, as
a check to show the light is working.
It should go out when the engine is
started.
If the light stays on, or comes on
while driving, there may be a
problem with the electrical charging
system. Have it checked by your
dealer. Driving while this light is on
could drain the battery. When this light comes on, or is
flashing, the Driver Information
Center (DIC) also displays a
message.
If a short distance must be driven
with the light on, be sure to turn off
all accessories, such as the radio
and air conditioner.
Malfunction Indicator
Lamp (Check Engine
Light)
This light is part of the vehicle’s
emission control on-board
diagnostic system. If this light is on
while the engine is running, a
malfunction has been detected and
the vehicle may require service. The
light should come on to show that it
is working when the ignition is on
and the engine is not running. See
Ignition Positions (Keyless Access)
0
208 or
Ignition Positions (Key Access)
0 210.
Malfunctions are often indicated by
the system before any problem is
noticeable. Being aware of the light
and seeking service promptly when
it comes on may prevent damage.
Caution
If the vehicle is driven continually
with this light on, the emission
control system may not work as
well, the fuel economy may be
lower, and the vehicle may not
run smoothly. This could lead to
costly repairs that might not be
covered by the vehicle warranty.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
140 Instruments and Controls
The DLC is under the instrument
panel to the left of the steering
wheel. Connecting devices that are
not used to perform an Emissions
Inspection/Maintenance test or to
service the vehicle may affect
vehicle operation. SeeAdd-On
Electrical Equipment 0322. See
your dealer if assistance is needed.
The vehicle may not pass
inspection if:
. The light is on when the engine
is running.
. The light does not come on
when the ignition is on while the
engine is off.
. Critical emission control systems
have not been completely
diagnosed. If this happens, the
vehicle would not be ready for
inspection and might require
several days of routine driving before the system is ready for
inspection. This can happen if
the 12-volt battery has recently
been replaced or run down, or if
the vehicle has been recently
serviced.
See your dealer if the vehicle will
not pass or cannot be made ready
for the test.
Brake System Warning
Light
MetricEnglish
This light should come on briefly
when the vehicle is turned on. If it
does not come on then, have it fixed
so it will be ready to warn you if
there is a problem.
If the light comes on and stays on at
start up, there is a brake problem.
Have the brake system inspected
right away. If the light comes on while driving,
pull off the road and stop carefully.
If equipped with electric brake
boost, vehicle speed may be limited
when the brake system warning
light comes on. The brake pedal
might be harder to push, or the
brake pedal may go closer to the
floor. It could take longer to stop.
If the light is still on, have the
vehicle towed for service. See
Towing the Vehicle
0424.
{Warning
The brake system might not be
working properly if the brake
system warning light is on.
Driving with the brake system
warning light on can lead to a
crash. If the light is still on after
the vehicle has been pulled off
the road and carefully stopped,
have the vehicle towed for
service.